A Periodontist had his hygenist perform deep cleaning and did it in two visits with a followup third visit. I kept asking how much was covered and he kept saying it should mostly be covered. I paid him $300 up front to cover my portion. He never did verify and should have told me he didn't . I got a bill for $1000 because it wasn't covered. Now he is threatening to sue me in limited jurisdiction so I would pay a lot more if I lose. What should I do?